Add CoreDisTools header

Add CoreDisTools header

CoreCLR uses the CoreDisTools library for utilities like GCStress
and SuperPMI. To aid these utilities, this change adds the
CoreDisTools header to CoreCLR repository.

This cleans up duplication of type/enum definitions in CoreDisTools
and CoreCLR sources, and provides for a cleaner way to use the
interface.

The understanding here is that CoreCLR defines the required
CoreDisTools interface, and will publish the header into the
cmake-install directory.

Any repository can pick up this header and supply implementations
for the imported functions. [Currently the only implementation
is the one that uses LLVM disassembler in the LLILC tree].

Two other changes:
1) Define TypeDefs for exported function types in cordistools.h
   to avoid duplicating the signature in importing code.
2) Move to the libcoredistools version 1.0.1, and use the new
   interface in disassembler.cpp